Hydrocarbon feedstock containing high molecular weight hydrocarbons is cracked by contacting it under elevated temperatures with a cracking catalyst whereby light distillates are produced. However, the cracking catalyst gradually deteriorates during this process. One cause of this deterioration is the deposition of metals, such as nickel, vanadium and iron, on the catalyst, which increases the production of hydrogen, dry gas and coke. At the same time the conversion of the hydrocarbons into gasoline is reduced. Thus, it is desirable to prevent or eliminate the adverse effects of such metal deposition, as by metals passivation, e.g., by contacting metals-contaminated catalyst with antimony-containing compounds and restoring the catalyst activity thereafter with conventional calcination techniques.